Go to www.snapnames.com and read their docs. If you want an account look around for the $49 promo deals found on some websites to sign up instead of paying $69 by signing up at their site.
www.namealerts.com has a permanent $49.99 option - saving $20 on each "snapback" - ( company attempts to register a name when owner fails to renew it and it expires, eventually to "drop" as available to the first person that grabs it). So far I have had 100% success using this method but there are some other options.